Interfolding of sheet material (e.g., napkins, paper towels, tissue, etc.) is frequently performed using a series of rolls that cooperate to sever web material into sheets, overlap the sheets, and interfold the overlapped sheets to form an interfolded stack of sheets. Certain of the rolls include a vacuum system having vacuum ports on the outer surface of the roll, which are selectively supplied with vacuum to hold and release the sheets during rotation of the roll.
In a typical prior art system, a roll is internally drilled to route air flow from the roll surface to the roll sides. Stationary side valves are spring loaded against the roll sides to encapsulate the vacuum ports on the rolls sides. Each side valve is in the form of a plate which has a rectangular cross section, circular cavity machined into the side of the valve face, which bears against the roll side. The valve cavity matches the ports in the roll side. The valve cavity intersects a perpendicular supply port that interfaces the valve with a vacuum supply system. Partial segment slugs are positioned in the valve cavity, so as to correspond to vacuum on/off points in rotation of the roll. The slugs are held in position with bolts through slots in the outer sides of the valve.
While a system of this type functions adequately, it requires the interfolding machine to be stopped and the slugs manually moved within the slots in order to alter the on/off points of the vacuum supplied to the roll surface. Furthermore, the thickness of the side valve plate defines a bottleneck that limits the strength of the vacuum that can be supplied to the surface of the roll.